this will be my last post about the 120, in respect to the good sir.
heartstone responds well to 120hz, i have it installed on my pc, i play it, it takes only seconds to change the setting so it is very very easy to compare. even my wife (who has low interest) can notice it. and it's not just for the smoothness, i just favor having 120 then dip a little lower so it is still smooth, than push it 60fps then dip to 30 sometimes.
if you haven't own something more than 60hz then you can only answer based on what you read. hey, i myself cannot here much difference when using expensive headsets with amps and all, my ears are just not sensitive enough, so i don't really appreciate it
edit: i am not saying that i can "see" when a 120 goes down to 110, no, but 60 vs 120, yeah it is noticeable.
just try, set to 60, drag around a notepad or something, set to 120 and do the same. it pays well in first person shooters where you do quick turns